Briefly stated, the present invention relates to seat belt webbing, and more particularly to an improved seat belt webbing having low longitudinal stiffness and reduced friction characteristics to assist in retraction and extraction of the seat belt.
Seat belt (also called safety belt) systems have evolved significantly as these systems have become standard equipment in all types of automotive vehicles. Different designs of seat belts have been provided for various types of systems, depending upon the properties desired. It has been recognized that in order to provide an effective seat belt system, it is preferable that the seat belt webbing have various desirable characteristics.
Desirable characteristics of seat belt webbing typically include: good lateral stiffness to help prevent roping or twisting of the seat belt, such as within the "D" ring upon extraction or retraction which could lead to a malfunction of the seat belt system; low longitudinal stiffness to reduce the retraction and extraction of the seat belt into and out of the seat belt winding mechanism; good abrasion resistance to help ensure a long product life; and passenger comfort to promote product use.
Passenger comfort is often associated with reduced spring tension in the winding mechanism. The winding mechanism is used to retract the seat belt when not in use, and typically include a spool upon which the webbing is coiled as well as a spring for applying tension to the seat belt as it is extracted so that it can be automatically retracted when released by the user. The spring tension must be high enough so that the seat belt webbing will be fully retracted with reliability, but the spring tension must not be so great that it causes discomfort to the user as the seat belt is being fastened and worn. A main force resisting retraction of the seat belt webbing is friction generated between the surface of the seat belt webbing and the guide members of the seat belt restraint system through which it passes. All of these traits are now being considered more by purchasers of automobiles when evaluating overall automobile quality, and accordingly, are being carefully evaluated by manufacturers for improvement.
It would be desirable to provide a woven seat belt webbing having all of the desired characteristics as set forth above, as well as a seat belt webbing which permits a winding mechanism with reduced spring tension to be used in order to increase user comfort.